: We have a 1920's house with (I believe) original fixtures in the shower (American Standard, dual valve). We can't seem to take set the temperature to a nice mix and have it stay there. The shower will run hot (almost scalding) so you turn down the hot and up the cold a little. Then it runs cold. Etc. This morning I just turned down the cold altogether and had about 5-10 seconds of ice water coming out.

: Should I replace the valves? The whole assembly? I have new copper risers that I can tap into, would that help/solve this issue?

: I hate to cut into walls before getting expert opinions, so thanks in advance. The plumbing from the risers up is all original galvanized, but the main service and basement piping is all copper. Hot water heater is brand new, 75 gallon.